BMS248 Lecture 12 - Drosophila Olfactory Learning

Question 1

In classical conditioning when should the conditioned stimulus occur in regards to the unconditioned stimulus?

Answer 1

The conditioned stimulus shoiuld coincide with or precede the unconditioned stimulus - I.e. the conditioned stimulus predicts the unconditioned stimulus

Question 2

What is the drosophila olfactory pathway beginning at the odour?

Answer 2

1. Odour
2. Olfactory receptor neurons
3. Projection neurons (2nd order)
4. Kenyon cells (3rd order) - CS
5. Dopaminergic neurons - US
6. Mushroom body output neurons

Question 3

3rd order neurons (Kenyon cells) sample what to respond to respond selectively to odours?

Answer 3

2nd order - projection neurons

Question 4

What do drosophila Kenyon cells receive input from? What do they require to fire?

Answer 4

Multiple projection neurons
Require multiple simultaneous inputs to fire from projection neurons - sparse coding

Question 5

What type of memory are Kenyon cells the site of?

Answer 5

Associative memory storage - DA + KC = plasticity at the synapse

Question 6

What does the GAL4/UAS system allow you to artificially express in specific cells?

Answer 6

Arbitrary transgenes - GAL4 binds to UAS which recruits transcription factors to initiate transcription downstream of UAS

Question 7

What is the split-GAL4 system? Advantages?

Answer 7

Has an extra activation domain which is required to drive gene expression - increased specificity

Question 8

What cell type is the mushroom body made up of?

Answer 8

Kenyon cells

Question 9

Kenyon cell axons are subdivided into compartments by
innervation by what two types of neurons?

Answer 9

1. Mushroom body output neurons (MBONs)
2. Dopaminergic neurons (DANs)
   - innervation patterns match

Question 10

How are Kenyon cell axons subdivided?

Answer 10

One-to-one matching of dopaminergic neurons (DANs) and mushroom body output neurons (MBONs), tiling axons of Kenyon cells

Question 11

Some MBONs lead to what BEHAVIOUR when activated optogenetically?

Answer 11

Approach/avoidance behaviour

Question 12

Some DANs, when activated optogenetically can entrain what MEMORY?

Answer 12

Aversive or appetitive memory

Question 13

Reward DANs encode the same areas as what kind of MBONs?

Answer 13

Reward DAN - Avoidance MBON
Punishment DAN - Approach MBON
(Opposite)

Question 14

During learning, dopamine signalling has what effect on synapses between KCs and MBONs?

Answer 14

During learning, DANs locally depress synapses between KCs and MBONs - leading to the ‘wrong’ action.
I.e. avoidance behaviour arises from a weakening of synapses on ‘approach’ MBONs

Question 15

What is the difference between forward and backward pairing?

Answer 15

Forward pairing - CS before US - e.g. odour then reward
Backward pairing - US before CS

Question 16

In FORWARD pairing (i.e. learning) what happens to the response at KC-MBON synapses?

Answer 16

Depressed - decrease in respond after pairing - due to cAMP

Question 17

In BACKWARD pairing what happens to the response at KC-MBON synapses?

Answer 17

Potentiate - increase in response after pairing - due to Ca2+

Question 18

What are the two types of Kenyon cell dopamine receptors and their signalling pathways?

Answer 18

1. DopR1 - Gs - ^ cAMP - aquisition
2. DopR2 - Gq - ^ ER Ca2+ - forgetting

Question 19

What pairing is DopR1 associated with?

Answer 19

Acquisition of memory - forward pairing - depression

Question 20

What pairing is DopR2 associated with?

Answer 20

Forgetting memory - backward pairing - potentiation

Question 21

What can be used to measure the activity of DopR1?

Answer 21

EPAC - sensor for cAMP

Question 22

What can be used to measure the activity of DopR2?

Answer 22

ER-GCaMP - measures ER calcium

Question 23

What is released during forward conditioning compared to backward?

Answer 23

cAMP released during both forward and backward conditioning.
Whereas Ca2+ release only for backward.

Question 24

ER Ca2+ release is only allowed if IP3 –> Ca2+ - how?

Answer 24

The channel is a coincidence detector - calcium locks channel into a closed position if Ca –> IP3 - order of events

Question 25

How is the insect mushroom body similar to cerebellar like structures?

Answer 25

1. Projection neurons = Mossy fibres
2. Kenyon cells = Granule cells
3. DANs = Climbing fibres
4. MBONs = Purkinje cells

Question 26

Cerebellum mediates what? How is this similar to the mushroom body?

Answer 26

Mediates motor learning - partly about correcting ‘wrong’ movements
It is a common structure for ‘error correction’